Automatic carbon determinator



Nov. 29, 1960 E. L. BENNET ETAL 2,962,360

AUTOMATIC CARBON DETERMINATOR Filed Aug. 22, 1958 2 Sheets-Sheet 1 Nov. 29, 1960 E. L. BENNET ETAL ,96 60 AUTOMATIC CARBON DETERMINATOR Filed Aug. 22, 1958 2 Sheets-Sheet 2 N V EN TORS. W

@952. gfimmg m AUTOMATIC CARBON DETERMINATOR Eugene L. Bennet and William C. Rohn, St. Joseph, and Howard J. Schmitt, Benton Harbor, Mich., assignors to Laboratory Equipment Corporation, St. Joseph, Mich., a corporation of Michigan Filed Aug. 22, 1958, Ser. No. 756,628

6 Claims. (Cl. 23-253) The present invention relates to the art of quantitative chemical analysis, and has particular reference to apparatus for automatically determining the carbon content of a combustible sample.

The principal object of our invention is to provide apparatus for determining the carbon content of an analytical sample, such as iron and steel, and including such refractory substances as carbides and the like, without attention from an operator other than the insertion of a weighed sample into the apparatus and a reading of the final result.

Still another object is to accomplish the above by novel apparatus which is highly accurate and which accomplishes the determination quickly, usually within less than four minutes.

Yet another object is to provide apparatus for accomplishing the above without the requirement of technical proficiency from the operator.

Other objects and advantages will become apparent from the following description of a preferred embodiment of our invention which is illustrated in the accompanying drawings.

In the drawings, in which similar characters of reference refer to similar parts throughout the several views,

Fig. 1 is a diagrammatic representation of the principal mechanical portion of the apparatus;

Fig. 2 is a circuit diagram of the electrical equipment used for the control and operation of the mechanical portion of the apparatus; and

Fig. 3 is a diagrammatic developed view of the pertinent portion of a sequence timer which is used as an element in the organization.

In general, the apparatus of the present invention operates by burning a small sample-for instance, one gram or one-half gramof the substance to be analyzed in a stream of pure oxygen in an induction furnace of the type described in US. Patent No. 2,809,100, issued to George J. Krasl on October 8, 1957, for Combustion Analyzer. The apparatus forming the subject matter of that patent is indicated at in Figs. 1 and 2 of the drawings, and briefly consists of a high frequency induction furnace which, when energized, heats a sample to be analyzed, placed in a small crucible at the center of the induction field, extremely rapidly to a temperature above that at which the same will burn in pure oxygen. The oxygen is blown against the sample in the form of a jet so as to achieve a high order of turbulence and the sample to be analyzed burns extremely quickly so as to atent form various oxide products including carbon dioxide ice ard volume of gas which consists of the carbon dioxide together with an excess of oxygen, and then removing the carbon dioxide from the mixture and measuring the volume of the remaining gas. The loss of volume between the two measurements is representative of the quantity of carbon dioxide originally present and this quantity can be read directly in terms of percent carbon if a one gram sample is used. In the event that a half gram sample is used, the percent result, which is read directly from the apparatus, is simply doubled.

Referring more specifically to Fig. 1 of the drawings where the mechanical portion of the apparatus is shown, it will appear that the furnace 10 previously mentioned receives its oxygen supply from a source 14. This source will ordinarily consist of the usual high pressure oxygen cylinder including a two stage pressure regulator, a flow regulating valve, an oxygen purifying train, and a flow meter, so that pure oxygen can be caused to flow through the furnace continuously at a rate of from 0.3 to 4 liters per minute, the usual rate being about 1.5 liters per minute. Products of combustion are taken from the furnace into a line 16 containing a sulfur and dust trap and catalyst furnace for changing carbon monoxide to carbon dioxide, all indicated generally at 12, this line being vented to the atmosphere by way of 'a'normally open valve at 18. Normally, therefore, when the apparatus is in general use, oxygen slowly flows through the furnace and to the atmosphere, thus continuously sweeping the combustion portion of the apparatus clear of contaminating gases.

The line 16 has a branch 20 containing a valve 22, this branch leading to the atmosphere by way of a valve 24. A branch 26 of the line 20 extends downwardly through a float valve 28 to the top of a glass bulb '30 having a depending buret 32. Line 20, and hence the interior of the bulb 30, is also connected by a line 34 containing a valve 36 to the top of a carbon dioxide absorbent pipette at 38. The line leading to the pipette is also connected by a branch 40 to one end of a U tube 42, the other end of which is connected to the atmosphere by way of a valve 44. a

The pipette 38 consists of a bulb or inner chamber 45 having a float valve 46 at the top thereof, the. lower end of the bulb 45 having a downwardly extending stem 48 which is open at the bottom. This inner chamber 45 is surrounded by an enclosing envelope 50 and the system has sufficient solution therein so that as gas is forced into the top of the apparatus, so as to displace liquid downwardly in the inner chamber 45, this liquid flows out at the lower end of the stem 48 and rises Within the enclosing chamber 50. Air above the liquid in chamber 50 is vented to the atmosphere through an opening at 51. Conversely, as gas is withdrawn by way of the line 34, liquid flows from the outer chamber into the inner chamber and rises therein until it causes the float within the float valve 46 to rise and shut off communication between the inner chamber 45 and the line 34.

The temperature within the buret is indicated by a thermometer at 52, and although it is not shown, the buret is preferably water jacketed so that, by circulating water through this jacket at a varying rate, the temperature within the buret may be maintained substantially constant.

The lower end of the buret 32 is connected to a tube 54 leading to the lower portion of a leveling bottle 56, the tube 54 having a short branch 58 with a stopper in the open end thereof, the stopper, in turn, having a metal electrode 60 passed therethrough so that the innerend is brought into contact with any solution present in the line 54. If desired, this electrode and those to be mentioned presently may be sealed in the glass wall.

The mouth of the leveling bottle 56 has a stopper through which are passed two metal electrodes 62 and 64 with the electrode 62 extending downwardly into the bottle slightly farther than the electrode 64, so that liquid rising within the bottle 56 will be brought into contact with the electrode 62 and, upon a slight additional rise, will touch electrode 64. A tube 68 also passes downwardly through the stopper in the mouth of the bottle 56 so as to communicate at one end with the interior of the bottle, the other end being connected to a line 70 leading to the atmosphere by way of a valve 72 of relatively large capacity, and also to the atmosphere by way of a valve 74 of low capacity, this low flow rate characteristic being indicated diagrammatically by the restriction at 7 6. Another branch of the line 70 leads through a valve 7 8 to a source of oxygen under low pressure which ordinarily will be the same source 14 connected to the furnace 10.

All of the valves mentioned above are normally closed except the two float valves 28 and 46 and the normally open atmospheric valve 18. Other than the float valves, the valves are electromagnetically actuated as follows. Electromagnet 80 is connected to shift valves 18 and 22 together so that when this magnet is energized, valve 18 is closed and valve 22 opened. Electromagnets 82 and 84, when energized, open respectively valves 24 and 36 which, in general, control fiow between the buret and the pipette. Valve 44 is opened by energizing electromagnet 86, and valves 72, 74 and 78 are opened respectively by magnets 88, 90 and 92.

In conditioning this portion of the apparatus for use, the bottle 56 is filled with water acidified with sulphuric acid and containing a dye or other handy coloring agent to make the level thereof more readily apparent, this coloring agent commonly taking the form of a pH indicator such as methyl orange which turns red in acid solution. The filling is concluded when the liquid level rises to a zero mark near the bottom of the buret indicated at 94 with both sides of the system at atmospheric pressure. With the stopper in the mouth of the bottle, the electrodes 62 and 64 are adjusted, if necessary, so that the end of electrode 62 is somewhat beneath the surface of the liquid, while the electrode 64 just makes contact with the liquid surface. A precise adjustment to the zero condition is facilitated by slightly lowering or raising the bottle 56 upon an adjustable support.

The capacity of the bottle 56 should be somewhat greater than that of the buret and bulb 30, so that by displacing the liquid in the bottle downwardly and through the passage 54 into the buret, the liquid level in the buret can be elevated until it strikes the float valve 28 which thereupon automatically closes. At this juncture there should still be sufficient liquid in the bottle 56 to prevent oxygen from entering the passage 54.

The pipette is partially filled with a mixture of potassium hydroxide and water such that when the inner chamber 44 is full of liquid to the float valve 46, there will still be sufficient liquid in the outer chamber 50 to cover the lower end of the downwardly extending stem 48. Thus gas in the buret and bulb 30 can be displaced over into the inner chamber of the pipette by forcing the liquid from the bottle 56 into the buret by opening valve 36 and closing valves 22 and 24. Carbon dioxide in the gas mixture displaced into the pipette is removed from the mixture by the potassium hydroxide solution, and in order to facilitate the liquid to gas contact, the inner chamber 45 of the pipette is loosely filled with a mass of Wire, glass or plastic rods or beads or like substance having a large surface area.

About half way up one leg of the U tube 42 a pair of electrodes 96 and 98 extend through the side wall so as to have their ends exposed within the tube. This tube is filled with an electrolyte such as a dilute solution of sulphuric acid or potassium hydroxide, for instance, to a level such that, with atmospheric pressure prevailing in both legs of the U tube, the liquid level therein rises sufficiently to submerge the lower contact 98 and just touch the contact 96.

On Fig. 2 of the drawing, the valve operating solenoids have been indicated across the top and identified by the same numerals used on Fig. 1. Similarly, the U tube 42 and bottle 56, including their electrodes, have been diagrammatically indicated at the left hand edge near the bottom, the induction furnace forming a portion of Fig. 1 being indicated at 10.

In the circuit diagram of Fig. 2 the two sides of the line adapted to be connected to an ordinary alternating current volt supply are, for convenience, indicated by the letters A and B. One of these leads (in the drawings, the lead B) is switched, as at 100, so as to turn the equipment on and oif. Another switch 102 connected to the line -B is used for turning on and off the power supply to an electric motor 104 which drives a small liquid pump. The motor is arranged to be speed regulated by means of a variable transformer 106 across the line. This pump is for the purpose of circulating water through the water jacket previously mentioned, which encloses the buret and bulb so as to maintain the temperature substantially constant. It is separately switched since it may not be needed,- particularly in modern air-conditioned laboratories where the room temperature is substantially constant.

An electric motor driven cycle timer is indicated at 108 and has one side of its motor connected by the lead 110 to the line A. As will appear presently, at the beginning of the cycle of operation of the apparatus the motor 108 will be energized. Although different arrangements could be used, in the present example it drives a rotating drum or equivalent mechanism through a cycle of three minutes duration, or at a rate of two degrees of drum rotation per second, and shifts the drum from one position to the next with a snap action. The drum of this apparatus is shown in developed form in Fig. 3 where it will be understood that the cycle begins at the left hand edge and progresses toward the right through the eight major positions specified across the bottom of the figure.

The rotating drum controls seven switches, preferably of the snap action type, indicated in order on Fig. 2 beginning at the top by the numerals 111, 112, 113, 114, 115, 116 and 117. These same numerals are arranged vertically on Fig. 3 to indicate the path of drum mounted control elements which are related to each of these switches. In each path the black areas indicate elements for actuation of a particular switch, whereas white areas indicate the normal or relaxed condition of the switch. The drawing of Fig. 2 shows these switches in the positions they assume at the end of the cycle, or, in other words, position 8 as shown in Fig. 3. Thus, in position 8 only switch 117 is actuated and, as will be explained presently, this terminates the cycle. When desired, the cycle is restarted by simply advancing the cycle timer one step to the position 1.

Under the conditions prevailing, therefore, just prior to the start of a new cycle of operation, the switches controlled by the cycle timer are as follows. Switch 111 is open and will, when closed, connect the line B through the valve actuating electromagnet 82 to the other side of the line A so as to energize this electromagnet. Switch 112 is also open, and, when closed, connects the line B to line 120 leading to one end of a relay coil 122, the other end of this coil being connected to the other side of the circuit at line A. Contact 113 is in open condition, but when closed, will connect the line B to lead 124 which energizes the valve magnet 84. Contact 114 is open, but subsequently, when closed, energizes a lead 126 which is connected through the coil of valve magnet 92 to the other side of the line A. Switch 116 is open, but when closed connects the line B to a lead 128 which has relay connections to be described presently. Switch blade 115 is an element of a single pole double-throw switch, and in the relaxed condition, engages contact 130 connected to the side of the cycle timer motor 108 remote fromthe power lead A. In its actuated position, switch blade 115 engages switch contact 134 connected to lead 136 having relay and switch connection to be discussed presently. The blade 115 is connected by a lead 138 through a pilot light 140 to the power line A. Switch 117 has its blade connected to the power lead B, and the blade of this switch in the relaxed condition engages contact 142 connected to the previously mentioned lead 138. Since the cycle timer, however, is in the eighth position, thereby actuating switch 117, the blade thereof is disengaged from the contact 142 and engages contact 144 which, under these conditions, energizes a lead 146 connected through a pilot lamp 148 to the other side of the line A.

In the eighth position, therefore, the only portion of the circuit which is energized is the pilot lamp 148 which may be labeled to indicate that the apparatus is in standby condition. In any other position of the cycle timer, switch blade 117 will disengage contact 1144, thereby turning out the standby pilot light 148, and will engage contact 142, thereby energizing pilot lamp 140 which may be labeled to indicate that the apparatus is in operation. Also, except for a portion of position 2 as will be explained presently, power is supplied by way of line B, switch blade117, contact 142, lead 138, switch blade 115 (or a set of contacts in parallel therewith as will appear), contact 130, line 132, and motor 108 to the other side of the line A. The cycle timer motor, therefore, is in operation whenever the cycle timer is in any position other than position 8, with the exception noted above.

A gas tube connected as a thyratron is indicated at 150. This circuit includes a control transformer having a primary 152 connected across the power lines A and B, and a secondary 154 connected at one side to the power line A and across the tube heater. The cathode and screen are also connected to the A side of the line. Two resistors 158 and 160 in series are connected between the lead 156 (from the secondary to the heater) and the side of the power line indicated at A. The anode is connected by a lead 162 through a relay coil 164 to the B side of the power line. The common point between resistors 158 and 160, indicated at 166, is connected to the grid of the tube, and has other connections as will be indicated presently. The values of the resistors 158 and 160 are so chosen that the tube will conduct until a connection is established, as will appear presently for short circuiting the resistor 158.

Relay coil 122 operates a pair of moving switch con tacts indicated at 168 and 170 respectively. Contact 170 forms a portion of a single pole single-throw normally open switch, the stationary contact of which is indicated at 172. This stationary contact is connected to the A side of the power line, whereas the other contact 170 is connected to line 174 leading to the induction furnace 10, the other side of which is connected to the B side of the line. Therefore, energization of relay coil 122 closes contacts 170 and 172 so as to energize the furnace 10.

Contact 168 normally engages fixed contact 176 connected by line 178 to the lower electrode 98 in U tube 42. The upper contact 96 of the U-tube is connected by a line 180 to the lead 156 at the lower end of the voltage divider 158-J60. Relay moving contact 168, previously mentioned, is connected to the control grid of the tube, and a normally open contact 182 associated therewith is connected by a lead 184 to the uppermost electrode 64 in the leveling bottle 56.

The relay coil 164 in the anode circuit of the control thyratron operates three moving switch contacts indicated at186, 188, and 190. Switch 190 is normally closed, and in this condition connects together the lines 138 and 132 previously mentioned. Switch 188 is normally open'and, when closed, connects the previously mentioned line 120 to a line 192 which is connected to energize magnetic valve 80.

Moving switch contact 186 is connected to a branch of the previously mentioned line 128, and a stationary contact 194, normally in closed relationship thereto, is connected by a lead 196 through a relay coil 198 to the A side of the power line. Lead 196 is also connected by a branch to energize magnetic valve 86, the other side of this valve being connected to the power line A. A normally open contact 200 associated with moving contact 186 is connected by a line 202 to one side of the magnetic valve 90, the other side of this valve being connected to the A side of the power line.

Relay coil 198, previously mentioned, operates three moving contacts indicated at 204, 206 and 208. Of

these, switch 208 is normally closed and, in this condition, connects previously mentioned line 136 through magnetic valve 88 to the side of the power line at A. Switch 206 is also of the single pole single-throw variety and is normally closed, and in this condition connects electrode 62 in the leveling bottle 56 by way of line 210 with a lead 212 connected in turn with line 168 leading to the grid of the control tube. The remaim'ng switch 304 of this group is normally open, and when closed acts to interconnect previously mentioned lines 128 and 196.

Electrode 60 at the base of the leveling bottle 56 is connected by a lead 214 to the previously mentioned line 180. Two push button switches are indicated at 216 and 218, and the former, when actuated, connects the B side of the power line with lead 136 while the other switch 218 connects the B side of the power line to line 126 when actuated.

The system operates as follows: Assuming that the system is completely deenergized by open switches at the point and 102, and that the timer motor 108 has advanced the timing drum, forming the subject matter of Fig. 3, to the eighth position; if, now, switch 102 is closed, this will operate to energize the pump motor 104 to circulate water through the temperature control jacket of the bulb 30 and buret 32. The amount of water necessary to accomplish this purpose is controlled by the variable transformer at 106, and if no temperature control is needed the switch at 102 may be left open.

Upon closing the switch 100, the line B is energized, and this acts by way of contacts 117-144 to energize the pilot light at 148 so as to indicate that the apparatus is in the standby condition. The only other portions of the apparatus which are energized during this standby period are the primary 152 of the control transformer and relay coil 164 by conduction through the tube 150.

At this juncture, to conduct an analysis, and assuming that liquid is in the U tube 42 and in the leveling bottle 56 and the pipette 38, and assuming that there is a slow flow of oxygen passing through the furnace 10, a weighed sample of steel or'other material to be analyzed for its carbon content is placed in its crucible and elevated into the combustion position, all as is explained in the previously mentioned patent, and the cycle timer is moved so as to bring it to the first position. This releases switch 117 and actuates switches 111 and 114 as will be apparent from Fig. 3. The following occurs: Closing of switch 111 energizes magnetic valve 82 which opens the bulb 30 to the atmosphere, thereby insuring atmospheric pressure prevailing in the bulb 30 and buret 32. Closing of switch 114 energizes line 126 and magnetic valve actuator 92 which admits oxygen pressure to the top of the leveling bottle 56. This pushes the fluid in the leveling bottle downwardly and through the line 52'to the lower end of the buret 32. Liquid, therefore, rises in the buret and fills the bulb 30 until shut off at the float valve 28.

At the conclusion of 45 of rotation of the cycle timerthis is accomplished in about twenty-two and onehalf seconds-the cycle timer shifts to the second position, thereby opening switches 111 and 114 and closing switch 112. The vent to the atmosphere at valve 24 is therefore closed by deenergization of coil 82 and the oxygen pressure to the top of the leveling bottle 56 is removed. Closing of switch 112 energizes line 120, and hence solenoid 122. This acts to close contacts 170, 172 and, by way of line 174, energizes the induction furnace 10. The furnace, therefore, quickly rises to combustion temperature, and burning of the sample begins to take place.

Simultaneously, contact 168 engages contact 182, thereby connecting electrode 64 in the leveling bottle 56 by way of line 184 and contacts 182-186 with the grid of the control tube. Also, since contacts 286 are closed the grid of the control tube is connected by way of line 212, contacts 206, line 210, with the electrode 62 in the leveling bottle. However, inasmuch as the level of the liquid in the bottle 56 is low, the buret and bulb being full, electrodes 62 and 64 have no influence upon the circuit. Under these conditions the sample continues to burn, and since valves 36, 24, and 18 are closed, while valve 22 is open, the gaseous products of combustion and excess oxygen pass from the furnace by way of the sulphur trap, dust trap and catalytic furnace 12, valve 22, line 20, branch 26, to the top of the bulb 30.

About ten seconds before the completion of the number 2 position of the cycle timer, switch 115 will be actuated as is indicated in Fig. 3 of the drawings, thereby connecting the B side of the line by way of contacts 117-142 to the line 138, and hence by way of contacts 115-134 to line 136 which, by way of contacts 208, acts to energize magnetic valve actuator 88. This shifts valve 72 to the open position and exhausts the top of the leveling bottle to the atmosphere. At the same time, opening of switch contacts 115-130 deenergizes the cycle timer 108 so as to allow a complete burn-olf of the sample in the furnace and to permit the oxygen flow thereafter to sweep all of the products of combustion into the bulb 30 and buret 32.

When the level of the liquid in the leveling bottle 56 rises so as to be brought into contact with lower electrode 62, the control grid of the tube is connected by way of leads 168, 212, contacts 206, lead 210, electrode 62, the electrolyte in the bottle 66, the electrode 60, and line 180 to the lead 156. This deenergizes relay coil 164 and closes contacts 190. Since these contacts are in parallel with contacts 115-130, the cycle timer is restarted. The cycle timer then proceeds to complete the remaining ten seconds of the second position in the cycle.

At the end of the second period, contacts 112 are opened, thereby deenergizing solenoid 122. This turns olf the furnace by separating the contacts 170-172 and, by engaging contacts 168-182, places the control grid under the influence of leveling bottle electrode 64 by way of lead 184. Simultaneously, solenoid 80 is deenergized by opening of, the switch at 112. This removes the furnace from influencing the system by venting the furnace to the atmosphere at valve 18 and closing the valve 22. Closure of switch 111 energizes magnetic valve 82 which opens valve 24 to the atmosphere, thereby permitting the buret 32 and bulb 30 and the leveling bottle 56 to attain atmospheric pressure on both sides of the system, since the valve at 72 controlled by solenoid 88 is also open as previously mentioned.

When the timer advances to position 4, switch 113 is closed, thereby energizing solenoid 84 which opens valve 36 so as to connect the pipette 38 to the bulb 30.

About ten seconds before the conclusion of position 4, switch 116 will be closed by the cycle timer, thereby energizing solenoid 86 by way of contacts 186-194 so as to open valve 44 and vent the U tube 42 to the atmosphere. At this juncture, therefore, both arms of the U tube, the buret, the bulb 30 and the leveling bottle are all at atmospheric pressure with the buret filled with gas above the liquid which is at the zero position 94.

At the end of this period the timer advances to position 5, thus opening switch 111 and deenergizing solenoid 82, shiftingswitch 115 anddeenergizing solenoid 88, and

opening switch 116 which deenergizes solenoid 86. This closes valves 24, 72, and 44. The system is now sealed from the atmosphere. Switch 114 is closed, however, thereby energizing solenoid 92 which opens valve 78 so as to connect the oxygen supply 14 to the top of the leveling bottle 56. The liquid is, therefore, again forced into the buret and rises therein and through the bulb 30 until the float valve 28 closes.

The carbon dioxide from the sample mixed with oxygen is therefore emptied from the buret and bulb into the absorption pipette. As previously described, the carbon dioxide in the mixture is absorbed in the pipette by the potassium hydroxide solution therein.

At the conclusion of the cycle, when the timer moves to position 6, switch 114 is opened so as to deenergize solenoid 92 and close valve 78. This shuts off the oxygen supply to the leveling bottle 56. Solenoid 84 remains energized, however, so that communication between the buret and the pipette is maintained. Simultaneously, opening of contacts 115-130 stops the timer motor 108 since contacts are separated.

The liquid therefore recedes from the bulb 30 into the leveling bottle 56. When the liquid level in the bulb 30 reaches the top of the neck portion 32, the liquid in the leveling bottle engages contact 62. Since contact 62 is connected through contact 206 with the grid of thyratron tube 150, the thyratron is cut off and relay coil 162 is deenergized. This closes contacts 190 and retarts the timer motor 108. Cutting off of the thyratron also opens contacts 186-200, thereby deenergizing solenoid 90 so as to close valve 74. Coil 198 is also energized, and this opens contacts 206 and closes contacts 204.

Contact 284 acts to hold the circuit if contacts 186- 194 separate while the opening of contacts 206 removes the connection between the thyratron grid and electrode 62. Coil 164 is therefore reenergized and closes contacts 186-200 so as to open valve 74, thereby allowing a slow flow of air from the leveling bottle 56. It also opens contacts 190 and stops the timer motor. Also, valve 44 is held open by coil 86 energized by way of contacts 204.

The level of the liquid in the buret 32 therefore settles slowly until the level of the liquid in the U tube 42 reaches contact 96. This cuts off the thyratron and permits contacts 190 to reclose so as to restart the timer motor 108. Also opening of contacts 186-200 cuts off coil 90 and closes valve 74 so as to prevent the liquid from dropping lower in the buret 32.

The result of the above action is that receding of the liquid level in the buret 32 stops as soon as the uppermost electrode 96 is engaged by the liquid in the U tube or, in other words, when atmospheric pressure has been .established in both legs of the U tube. Thus the level of the liquid in the buret above its zero point is a true measure of the quantity of carbon dioxide in the original mixture since both prior to the time the gas was pushed into the pipette and after it has been returned to the bulb and buret, atmospheric pressure prevails Within the bulb 30. The level of the liquid in the buret, therefore, has no influence upon the end point, this being determined solely by the return of the gas pressure to its original condition. Shortly thereafter the cycle timer moves to the eighth position and shuts off the apparatus, as previously described.

Whenever it is convenient, the operator reads the volume of gas absorbed in the pipette from the liquid level in the buret. By standardizing upon a one gram sample, the indicia upon the buret can be made to read directly in percent carbon, and this is usually preferred.

If because of slow leakage, or if for any other reason when the operator returns to read the result from the buret, he should find that the level in the U tube 42 is not the same on each side, he can make a final correction by actuating the push button at 216 so as to energize solenoid 83 and open valve 72 to the atmosphere, thereby permitting the liquid to recede additionally in the buret 32 so as to raise the level of the liquid on the side of the U tube having the contacts 96 and 98, or, in the alternative, he can actuate the push button at 218 so as to energize solenoid 92 which opens valve 78 so as to supply oxygen pressure to the top of the leveling bottle 56, thereby raising the level of the liquid within the buret 32. Thus by actuation of one or the other of these two push buttons a balance can be quickly achieved, but it is not anticipated that this will ordinarily be necessary, these manual controls being provided to accommodate for exceptional circumstances where the operator may have been delayed in returning to the apparatus for an extended period.

From the above description of our invention, it will be seen that it is necessary merely for the operator of the equipment to weigh a sample, place it in the combustion crucible, and elevate it into position within the furnace, after which the cycle timer is advanced to its starting position. Thereafter no attention on the part of the attendant is necessary, and after the cycle timer has stopped operating-at this juncture pilot light 148 will be energized and light 140 extinguished-he can return whenever it is convenient and take the final reading from the buret and insert a new sample and start a new cycle of operation.

From the above description of our invention it will be appreciated that changes may be made without departing from the spirit and scope of the invention, and that therefore the scope of this invention is to be measured by the scope of the following claims.

Having described our invention, what we claim as new and useful and desire to secure by Letters Patent of the United States is:

1. In an automatic carbon determinator, furnace means for burning a sample to be analyzed in an oxygen atmosphere to convert the carbon therein to carbon dioxide mixed with an excess of oxygen, the last said means operating when electrically energized, a first container for holding a fixed quantity of gas at atmospheric pressure, a second container adapted to contain all of the gas held by the first said container and to remove any carbon dioxide therefrom, first conduit means connecting the burning means to the top of the first container means, second conduit means interconnecting the tops of said first and second container means, first and second electrically actuated shutoff valve means in said first and second conduit means respectively, differential pressure actuated means connected to be responsive to the differential pressure between said first container means and the atmosphere and to actuate an electric switch connected thereto when said differential pressure is substantially zero, cycle timer means adapted to time a cycle of operation when energized, electrically actuated means for forcing liquid into and withdrawing liquid from the lower end of the first container means, first and second electrically actuated valve means for venting said burning means to the atmosphere and for venting said first container means to the atmosphere respectively, and circuit means interconnecting said cycle timer, said valves, said differential pressure switch, said burning means, and said liquid forcing means to open both said vent valves and to force liquid into the first said container and displace all of the gas therein, subsequently to close both said vent valves and to open said first conduit valve and energize said burning means to displace liquid in said first container by gas from said burning means until said first container holds almost said fixed quantity of gas, subsequently to close said first conduit valve and open both said vent valves and to complete the filling of said first container with gas at atmospheric pressure and to open said second conduit valve and then close said second vent valve and to actuate said liquid forcing means to fill said first container with liquid to transfer said fixed quantity of gas from said first container to said second container, subsequently to actuate said forcing means to withdraw liquid from said first container to return the gas from said second container to said first container, means to interrupt said withdrawal of liquid when said differential pressure responsive switch is actuated by zero differential pressure, and means including said cycle timer for subsequently deenergizing said cycle timer.

2. In an automatic carbon determinator, furnace means for burning a sample to be analyzed in an oxygen atmosphere to convert the carbon therein to carbon dioxide mixed with an excess of oxygen, the last said means operating when electrically energized, a first container for holding a fixed quantity of gas at atmospheric pressure, a second container adapted to contain all of the gas held by the first said container and to remove any carbon dioxide therefrom, first conduit means connecting the burning means to the top of the first container means, second conduit means interconnecting the tops of said first and second container means, first and second electrically actuated shutoff valve means in said first and second conduit means respectively, sensitive differential pressure actuated means connected to be responsive to the differential pressure between said first container means and the atmosphere and to actuate an electric switch connected thereto when said differential pressure is substantially zero, means for normally desensitizing said differential pressure actuated means, electrically operated means for counteracting said desensitizing means when operated, cycle timer means adapted to time a cycle of operation when energized, electrically actuated means for forcing liquid into and withdrawing liquid from the lower end of the first container means, first and second electrically actuated valve means for venting said burning means to the atmosphere and for venting said first container means to the atmosphere respectively, and circuit means interconnecting said cycle timer, said valves, said differential pressure switch, said counteracting means, said burning means, and said liquid forcing means to open both said vent valves and to force liquid into the first said container and displace all of the gas therein, subsequently to close both said vent valves and to open said first conduit valve and energize said burning means to displace liquid in said first container by gas from said burning means until said first container holds almost said fixed quantity of gas, subsequently to close said first conduit valve and open both said vent valves so as to establish atmospheric pressure in said first container and vent said burning means to the atmosphere and then to open said second conduit valve and then close said second vent valve and to actuate said liquid forcing means to fill said first container with liquid to transfer said fixed quantity of gas from said first container to said second container, subsequently to actuate said forcing means to withdraw liquid from said first container to return the gas from said second container to said first container, means to slow down said withdrawal of liquid and to operate said counteracting means when the liquid in the first said container reaches a predetermined level indicative of an approach to atmospheric pressure and to interrupt said withdrawal of liquid when said differential pressure responsive switch is actuated by zero differential pressure, and means including said cycle timer for subsequently deenergizing said cycle timer.

3. In an apparatus having a closed vessel for containing an unknown quantity of gas to be measured volumetrically at atmospheric pressure, means to admit liquid to the lower end thereof so as to vary the gas pressure by adjusting the liquid level and hence the gas volume in said vessel, said vessel having a scale to facilitate determining the quantity of gas in said vessel from the level of the liquid therein, said means including, a container for liquid, conduit means connecting the lower portion of said container to the lower portion of said vessel, said container being at an elevation such that liquid normally flows between said vessel and said container, electrically actuated valve means adapted when actuated to stop the flow of liquid between said vessel and said container, means providing a pair of upstanding interconnected liquid columns with an isolated gas space above the liquid in each column, conduit means connecting one of the last said isolated gas spaces to said vessel near the top thereof, means venting the other of the last said isolated gas spaces to the atmosphere, switch means actuated by the liquid level in said columns when the level in both columns is substantially the same, and electric circuit means interconnecting said switch means and said valve means to actuate said valve means upon actuation of said switch means.

4. In an apparatus having a closed vessel for containing an unknown quantity of gas to be measured volumetrically at atmospheric pressure, means to admit and withdraw liquid to and from the lower end thereof so as to vary the gas pressure by adjusting the liquid level and hence the gas volume in said vessel, said means in cluding means forming a liquid drain connected to the lower portion of said vessel, electrically actuated valve means adapted when actuated to stop the flow of liquid from said vessel by way of said drain, means providing a pair of upstanding liquid containers interconnected below their liquid levels, conduit means connecting one of the last said containers above the liquid level therein with the upper portion of said vessel, means venting the other of the last said containers to the atmosphere, switch means actuated by the liquid in the last said containers when the level in both of the last said containers is substantially the same, and electric circuit means interconnecting said switch means and said valve means to actaute said valve means upon actuation of said switch means.

5. In an apparatus having a closed vessel for containing an unknown quantity of gas and in which means is provided to admit and withdraw liquid to and from the lower end thereof so as to vary the gas pressure by adjusting the liquid level and hence the gas volume in said vessel, said means including means forming a liquid drain connected to the lower portion of said vessel, means adapted when actuated to slow the flow through said drain, electrically actuated valve means adapted when actuated to stop the flow of liquid from said vessel by 12 way of said drain, means providing a pair of partially filled upstanding liquid containers interconnected below their liquid levels, conduit means connecting one of the last said containers above the liquid level therein with said vessel, means venting the other of the last said containers to the atmosphere, valve means normally closing the last said vent, means for opening the last said valve means and for actuating the slow flow means when the liquid level in said vessel drops to a predetermined level, switch means actuated by the liquid in the last said containers when the level in both of the last said containers is substantially the same, and electric circuit means interconnecting said switch means and the first said valve means to actuate the first said valve means upon actuation of said switch means.

6. Gas analysis apparatus comprising a first container for holding a fixed quantity of mixed gas at atmospheric pressure, a second container adapted to contain all of the gas held by the first said container and to remove a constituent gas from the mixed gas, conduit means interconnecting the upper portions of the first and second containers, means for forcing liquid into the lower por tion of said first container to transfer gas from said first container to the second container, drain means for draining liquid from said first container to transfer gas from the second container back to said first container, automatic valve means adapted to stop the flow through said drain means when actuated, means providing a pair of partially filled upstanding liquid containers closed at the top and interconnected below their liquid levels, conduit means connecting one of the last said containers above the liquid level therein with the upper portion of the first said container, means venting the other of the last said containers to the atmosphere, means actuated by the liquid in the last said containers when the level in both of the last said containers is substantially the same, the last said means being adapted when actuated to actuate said automatic valve means.

References Cited in the file of this patent UNITED STATES PATENTS 1,919,861 Rodhe July 25, 1933 

1. IN AN AUTOMATIC CARBON DETERMINATOR, FURNACE MEANS FOR BURNING A SAMPLE TO BE ANALYZED IN AN OXYGEN ATMOSPHERE TO CONVERT THE CARBON THEREIN TO CARBON DIOXIDE MIXED WITH AN EXCESS OF OXYGEN, THE LEAST SAID MEANS OPERATING WHEN ELECTRICALLY ENERGIZED, A FIRST CONTAINER FOR HOLDING A FIXED QUANTITY OF GAS AT ATMOSPHERE PRESSURE, A SECOND CONTAINER ADAPTED TO CONTAIN ALL OF THE GAS HELD BY THE FIRST SAID CONTAINER AND TO REMOVE ANY CARBON DIOXIDE THEREFROM, FIRST CONDUIT MEANS CONNECTING THE BURING MEANS TO THE TOP OF THE FIRST CONTAINER MEANS, SECOND CONDUIT MEANS INTERCONNECTING THE TOPS OF SAID FIRST AND SECONAD CONTAINER MEANS, FIRST AND SECOND ELECTRICALLY ACTUATED SHUTOFF VALVE MEANS IN SAID FIRST AND SECOND CONDUIT MEANS RESPECTIVELY,DIFFERENTIAL PRESSURE ACTUATED MEANS CONNECTED TO BE RESPONSIVE TO THE DIFFERENTIAL PRESSURE BETWEEN SAID FIRST CONTAINER MEANS AND THE ATMOSPHERE AND TO ACTUATE AN ELECTRIC SWITCH CONNECTED THERETO WHEN SAID DIFFERENTIAL PRESSURE IS SUBSTANTIALLY ZERO, CYCLE TIMER MEANS ADAPTED TO TIME A CYCLE OF OPERATION WHEN ENERGIZED,ELECTRICALLY ACTUATED MEANS FOR FORCING LIQUID INTO AND WITHDRAWING LIQUID FROM THE LOWER END OF THE FIRST CONTAINER MEANS, FIRST AND SECOND ELECTRICALLY ACTUATED VALVE MEANS FOR VENTING SAID BURNING MEANS TO THE ATMOSPHERE AND FOR VENTING SAID FIRST CONTAINER MEANS TO THE ING SAID CYCLE TIMER, AND VALVES SAID DIFFERENTIAL PRESSURE SWITCH, SAID BURING MEANS, AND SAID LIQUID FORCING MEANS TO OPEN BOTH SAID VENT VALVES TO SAID LIQUID FORCING INTO THE FIRST SAID CONTAINER AND DISPLACE ALL OF THE GAS THERIN, SUBSEQUENTLY TO CLOSE BOTH SAID VENT VALVES AND TO OPEN SAID FIRST CONDUIT VALVE AND ENERGIZE SAID BURNING MEANS TO DISPLACE LIQUID IN SAID FIRST CONTAINER BY GAS FROM SAID BURNING MEANS UNTIL SAID FIRST CONTAINER HOLDS ALMOST SAID FIXED QUANTITY OF GAS, SUBSEQUENTLY TO CLOSE SAID FIRST CONDUIT VALVE AND OPEN BOTH SAID VENT VALVES AND TO COMPLETE THE FILLING OF SAID FIRST CONTAINER WITH GAS AT ATMOSPHERIC PRESSURE AND TO OPEN SAID SECOND CONDUIT VALVE AND THEN CLOSE SAID SECOND VENT VALVE AND TO ACTUATE SAID LIQUID FORCING MEANS TO FILL SAID FIRST CONTAINER WITH LIQUID TO TRANSFER SAID FIXED QUANTITY OF GAS FROM SAID FIRST CONTAINER TO SAID SECOND CONTAINER SUBSEQUENTLY TO ACTUATE SAID FORCING MEANS TO WITHDRAW LIQUID FROM SAID FIRST CONTAINER TO RETURN THE GAS FROM SAID SECOND CONTAINER TO SAID FIRST CONTAINER, MEANS TO INTERRUPT SAID WITHDRAWAL OF LIQUID WHEN SAID DIFFERENTIAL PRESSURE RESPONSIVE SWITCH IS ACTUATED BY ZERO DIFFERENTIAL PRESSURE, AND MEANS INCLUDING SAID CYCLE TIMER FOR SUBSEQUENTLY DEENERGIZING SAID CYCLE TIMER. 